Intro arc

Prologue: In the year of 2XXX, a great occur wiping out 90% of the Earth population by a mysterious group who in hope trying to stop global warming. Since then, once per year, the group will come out from their hiding and wipe out the total population to the number 100000. The global warming is stop, after the tree and flower bloom in the place of building, most the human live their life in darkness fearing being killed in the annually war.